Seismic Performance And Fragility Analysis Of The Pile-supported Wharf In Liquefiable Soils

Port engineering is the transportation hub of waterway and highway,and wharf is one of the most important part of port engineering.Owing to its structural features and performance advantages,the pile-supported wharf is widely used in actual projects.With the proposal of the Belt and Road Initiative,China has built a large number of pilesupported wharves in countries along the 21 st Century Maritime Silk Road.However,most of these projects are located at the junction of the Europe plate,the Pacific plate and the Indian plate,in which the fully developed fault zone and liquefiable soils are widely distributed.In a word,the situation of those projects is very dangerous.In view of the severe seismic safety problems faced by pile-supported wharves,the research on seismic performance of the pile-supported wharf in liquefiable soils is very meaningful.In order to accomplish the mentioned work,this paper takes the all-vertical-piled wharf as the research object,and lots of finite element numerical models for a typical engineering are established.Through analyzing the data calculated by these models,the seismic responses and the seismic fragility of the pile-supported wharf are analyzed.The main research contents,methods and results are summarized as follows:Firstly,in order to explain the numerical method used to simulate the seismic reaction of the soil-pile group-superstructure system in liquefiable soils,the finite element model for a typical centrifuge test is established.In the process of modeling,a criterion for determining the stiffness parameters of pile elements is proposed,the friction effect and the end bearing effect provided by soils to piles are simulated,and the boundary effect of the soil box used in centrifuge test is described.By analyzing the differences between the test data and calculated data,the rationality of the method is verified and the causes of errors are discovered.Secondly,based on the numerical simulation method which has been verified in the Chapter 2,some finite element models for a typical engineering are established.By analyzing the calculated data,some important seismic responses of the pile-supported wharf are discovered,the performance indexes of seismic demand are selected and the vulnerable positions during earthquakes are determined.Subsequently,the influences of various factors on the seismic demand of the pile-supported wharf are analyzed,including peak ground acceleration,frequency characteristics of input ground motions,the input direction of ground motions,site inclination,load conditions and the embedded depth of the pile foundations.According to all the above findings,some suggestions on the design and construction of pile-supported wharves are put forward.Finally,with the help of numerical models established in the Chapter 3,mode analysis and pushover analysis of the pile-supported wharf are carried out.As a result,the damage evolution laws of the pile-supported wharf in the bending failure mode and the bending-shear failure mode are explored.What's more,the judgment criteria for each damage stage of the pile-supported wharf are determined.Based on the data obtained from incremental dynamic analysis,the relationship between the selected intensity measure(IM)and the selected engineering demand parameters(EDP)is discovered.According to all the above findings,a set of seismic fragility curves of the pile-supported wharf in liquefiable soils are deduced.At last,for the purpose of convenient application,the deduced seismic fragility curves are expressed as lognormal cumulative distribution functions.This article has good reference significance for the development of performancebased seismic design throry of pile-supported wharves in China.